A FRIEND of mine was talking to her mother on Sunday. Her mother had always been opposed to her daughter’s political activity. My friend was amazed to be congratulated on going on Saturday’s demonstration in London. She was even more amazed by what came next when her mother said, “But demonstrations are not enough. People need to do more.”

This sentiment is very widespread as people wake up in the morning and go to bed at night to images of bombers from Britain incinerating and burying alive people in Baghdad.

But on one count it is wrong. The protests so far have not been wasted. Never in history have there been such widespread, global demonstrations against a war as we saw at the end of last week. And they threaten the global US interests that lie behind the war.

The military strategist Karl von Clausewitz famously pointed out 200 years ago, “War is a continuation of politics by other means.” But rarely have politics been as central to the conduct of a war as the present one. The whole US strategy has been designed around two political assumptions. Firstly, that the Saddam regime is so unpopular that it will be unable to defend Iraqi cities.

Secondly, that the war will be over before protest movements internationally destabilise governments friendly to the United States – especially in strategically important parts of the Middle East, but also here in Britain, Italy and Spain.

These assumptions explain the attempted US rush to Baghdad, despite its generals’ fear that the strategy could easily go wrong. Yet both assumptions are already turning out to be wrong. Five days into the war there was little sign of the Iraqi Arabs rising up against Saddam in the south of the country.

Crowds in Iraq are hunting for parachuting US pilots, like British crowds hunted for German pilots during the Second World War, because they see them as the main enemy, not Saddam. And even the anti-Saddam Kurds are talking as much about fighting against Turks as fighting against Saddam’s army.

The overwhelming military hardware of the US might still be able to prevail, but the war could be much harder and longer than was first calculated. And any gains for US imperialism can be more than offset by its loss of influence and power elsewhere.

There are fears within the US establishment that an eventual victory in Baghdad could be accompanied by the disintegration of Iraq into warring fiefdoms run by Kurds, Turks and Shia Muslims influenced by neighbouring Iran, which is next on Bush’s “axis of evil” list.

The difficulties in Iraq translate directly to difficulties for the pro-US regimes of the region. Here the second US miscalculation, about the global anti-war movement, plays a central role. The Middle East regimes, with the partial exception of Lebanon, are all militarised dictatorships.

Their ruling classes and parties are tied into global capitalism and rely on repression to frighten those who do not share in their wealth from protesting. But that fear can disappear once substantial numbers demonstrate together on the streets, occupy the universities or strike in the factories.

People are encouraged to do such things in Cairo or Amman when they see TV images of giant protests in London, San Francisco, Madrid or Rome. The sense of a global movement strengthens protesters everywhere. So it is that advisers to the murderers in the White House and Downing Street warn that too much open carnage in Iraq can ignite uprisings elsewhere in the Middle East.

In effect, US generals are constrained in what they can do in the deserts of Iraq by what we do here. Meanwhile, Tony Blair has a big problem of his own. His gung-ho backing for Bush has not only upset those Old Labour types who believed Labour was a party of peace.

It has also caused deep splits among those who fervently backed him only a few weeks ago because they saw him as an apostle of a united capitalist Europe. He allied himself with the right wing Europhobe papers of Rupert Murdoch and Conrad Black to whip up hysteria against Jacques Chirac and Gerhard Schröder – and ruined the chances of a successful referendum on the euro in a couple of months time.

Euro enthusiasts like Guardian columnist Polly Toynbee are foaming at the mouth. They have come out against the war along with their Europhile friends like the Liberal Shirley Williams and the Tory Kenneth Clark. Blair may have won a parliamentary vote, but he sees his political future crumbling all around him.

So keep up the protests. Setbacks on the battlefield and protests internationally can still force Bush and Blair to abandon their barbarity in Iraq, just as the US abandoned its attempts to subjugate Vietnam nearly 30 years ago.

And they can certainly be made to think twice before embarking on another murderous adventure. That is a benefit for humanity as a whole that is well worth struggling for.